1. Field of the Invention
This invention relates to a method for producing a heavy crude oil from a subterranean formation and converting the heavy crude oil into a product distillate hydrocarbon stream suitable for pipelining and optionally a distillate diluent stream and recovering added values from the residual portions of the heavy crude oil as heat, electricity, steam or synthetic liquid hydrocarbons.
2. Description of Related Art
In many parts of the world heavy crude oils are available for production in remote locations. In such remote locations commonly available utilities such as electricity and steam may not be available at all or may be available only in short supply. In such instances, the only option may be to transport the heavy crude oil in a pipeline to a location from which it may be transported to a refinery. Many of the heavier components contained in the heavy crude oil may not be suitable for distillation into distillate hydrocarbon products and may eventually be converted into asphalt, petroleum coke or the like.
In less industrialized parts of the world there may be little market for such products. As a result the products may be of low value in the accessible marketplace. Alternatively, the heavier components may be blended with lighter oils to produce a heavy fuel oil product. Typically, the market value of such heavy fuel oils is relatively low, especially, when the value of the diluent oil as a distillate product is considered.
Such heavy crude oils in some instances, are so viscous that it may be difficult to recover the heavy crude oils from a subterranean formation initially without admixture of a hydrocarbon diluent with the heavy crude oil in the wellbore to reduce the viscosity of the heavy crude oil. Even if the heavy crude oil is at an elevated temperature in the subterranean formation which is high enough to result in a flowable heavy crude oil at the elevated temperature the heavy crude oil remains likely to cool and solidify in upper portions of the producing well, especially during any periods where production is stopped for an interval. Similarly the heavy crude oil is likely to cool and solidify in surface pipelines unless required temperatures and flowrates in the surface pipelines can be maintained. As a result typically distillate hydrocarbon diluents (or occasionally other diluents) are mixed with such heavy crude oils either during or after production and before pipelining to prevent solidification of the heavy crude oil in the pipeline.
Such heavy crude oils contain a much higher percentage of non-distillable components than lighter crude oils. Some such heavy crude oils may contain less than 50 weight percent distillable hydrocarbons.
The production and transportation of such heavy crude oils, especially in remote locations, requires that large quantities of hydrocarbon diluent be transported to the remote location via a pipeline, by truck or the like. This hydrocarbon diluent is expensive relative to the heavy crude oil even without considering the added transportation cost. The diluent when mixed with the heavy crude oil may result in a mixture which still contains as much as 45 weight percent residual (non-distillable) materials. Transportation of this residual material requires a larger pipeline and limits the production and transportation of the desired distillable components of the heavy crude oil. In some oil fields the total production volume may be limited by governmental regulation, pipeline capacity and the like. Desirably the hydrocarbon stream transported consists of distillable products. Even if transported to a refinery the residual materials are of little value and are typically charged to a petroleum coker or used as asphalt and the like. Typically such heavy crude oils also have a high metals content in the residual materials which reduces the value of any petroleum coke produced from such residual materials.
It is also desirable that electricity, steam or both, be available for operations at the remote production sites.
These considerations may result in many heavy crude oils at remote locations being uneconomical to produce and market. Accordingly, a continuing search has been directed to methods for producing such heavy crude oil, at remote sites and delivering valuable distillable hydrocarbons to refineries and the like economically.